18 VEGETATION IN COLORADO-HOLM. [MeM0IRS [vol T .'x1x: 



Chapter 4. 



NOTES ON THE PROBABLE LOCATION OF THE CENTERS OF DISTRIBUTION AND 

 DEVELOPMENT OF THE ALPINE SPECIES. 



In a previously published paper dealing with the genus Carex in Colorado * I have demon- 

 strated the fact that certain species of this genus are represented in mountains very remote from 

 each other — for instance, the Rocky Mountains, the European Alps, and the Himalayas — and 

 associated with more or less closely allied types. Carex alpina Vahl, C. atrata L. and C. stellidata 

 Good, for instance, show a remarkably wide geographical distribution and are accompanied 

 by species of the corresponding "greges." In regard to C. atrata this species is very rare in 

 the Arctic regions of Europe, but not infrequent in the mountains farther south. In the Rocky 

 Mountains it is accompanied by C. chalciolepis nob. and C. bella Bail, while a near ally C. ovata 

 Rudge abounds in the northeastern parts of this continent. In Europe C. atrata is, to some 

 extent, accompanied by two allies, C. nigra Gaud and C. aterrima Hppe. Finally, in the Hima- 

 layas we not only meet with several species that may be looked upon as representing immediate 

 allies of C. atrata but also with the species itself. If thus the association with allies in connection 

 with frequent occurrence and tendency to vary may throw any light upon the question relative 

 to the center of distribution or even of development of the respective species, it seems as if 

 C. atrata may have had more than one center; very likely one in the Rocky Mountains, another 

 in the European Alps, and a third one in the Himalayas. A like distribution and association 

 with allied types may be readily recorded from several of the other Alpine plants, whether 

 these be simply Alpine or Arctic-Alpine. Most of, if not all, the circumpolar species may be 

 excluded, since these undoubtedly originated in the Arctic mountains, a view held by Heer, 2 

 Nathorst (1. a), and several other authors. It seems natural to suppose that the same species 

 by migrating to stations remote from each other became modified so as to produce varieties, 

 and these becoming sufficiently constant and sometimes sufficiently distinct so as to deserve 

 rank of species. In other words, the new surroundings might be the cause of developing new 

 varieties or even species at several stations, more or less remote from each other, at the same 

 time as new centers of geographical distribution might be established. 



The hypothesis that the same species may have developed at several stations, hence from 

 more than a single individual, was proposed by Schouw: 3 "Eadem momenta cosmica easdem 

 plantas diversis in locis produxisse," and accepted by Agassiz, 4 Elias Fries, 5 and some other 

 writers. Alphonse De Candolle formerly 6 adopted and strenuously maintained Schouw's 

 hypothesis, but in his work, "Geographie botanique raisonn6e," he has in effect discarded it. 

 Linnaeus ' did not believe in more than one single center of development. According to him 

 each species had developed from a single individual or in dioecious species from a single couple 

 of individuals. Joseph Hooker, 8 Asa Gray, 9 and a number of recent authors were in favor of 

 the Linnean hypothesis as well as Alphonse De Candolle (1. c). The last of these authors, 

 De Candolle (Geogr. bot., p. 1116), explained the fact of certain species occurring at stations 

 remote from each other by the possibility of these having been formerly much more widety 

 distributed than at present, but separated from each other by change in climate or destruction 

 of continents. This explanation of De Candolle carries great weight and is acceptable, of 



i Am. Journ. of Sc, Vol. XVI. 1903. p. 40. 



1 Ueber die nivale Flora der Schweiz. 18S3. 



a Dissertatio de sedibus plantarum originariis. Copenhagen, 1816. P. 64. 



' Geographical distribution of animals. 1850. 



s Botaniska utflygter, vol.3. 1864. P. 114. 



» Fragment d'un discours sur la geographie botanique (Bull, univ. 1834). 



' De telluris incremento ( Amoen. acad., vol. 2, Stockholm, 1743). 



> Outlines of the distribution of Arctic plants (Transact. Liirn, Soc. vol. 23, 1S61, p. 251). 



• On the Botany of Japan (Mem. Am. Acad. Sci., vol.6, n. s., 1857, p. 444). 



